Radio receiving system



Patented June 26, 1928.

UNITED STATES P TENT OFFICE.

RUSSELL s. OHL, or NEW YORK, N. Y., AssIeNoR T AMERICAN TELEPHONE Ann" TELEGRAPH COMPANY, A CORPORATION orivnw YORK.

RADIO RECEIVING SYSTEM. 9

Application filed August 26', 1925. Serial No. 52.651.

This invention relates to signaling systems, and particularly to asystem for detectinga signal which issuperposedon a high frequency current.

One of the objects of this invention is to so relate a pair of high frequency oscillators to a circuit carrying a high. frequency current modulated in accordance with signals that the signals may be derived therefrom.

three high frequency currents together, one of said high frequency currents being modulated in accordance with signals, so that a band of intermediate frequencies results,

from which the signals may be selected,

While the novel features of this invention will be pointed out-with particularity in the appended claims, the invention itself, both as to its objects and features, will be better understood from the detailed description hereinafter following when read in connection with the accompanying drawing in which Figurel represents one embodiment of the invention, and Fig. 2 representsa modification of the arrangements of Fig. 1. 7 Referring to Fig. 1, the referencecharacter a represents an antenna which is con: nected to a counterpoise b by means of an inductance a. The antenna a, counterpoise]; so and the inductance ctogether form a circult which is adaptable for receiving high frequency currents of the order of 10,000 k1l0 cycles upon which are superposedlow frequency signals. An inductance d is loosely coupled to the inductance c and impresses the frequency of the receiving circult' upon the input circuit of a detectorD An oscillator is represented by the reference character 0 This oscillator, which is 40 capable of setting up oscillations of high frequency, for example, 10,050'k1locycles, is also connected to theinput circuit ofthe detector 1),. This oscillator may be of any well known type, but is preferably a vacuum tube oscillator. Another oscillator isrepresented by the reference character Q which oscillator may be a piezo-electric oscillator, or any other oscillator capable of setting up high frequency oscillations which 1 are constant in frequency within very narrow limits. This oscillator 0 is connected to a harmonic generator HG, or frequency multiplier,'so that the frequency of osc1lla= tions of the oscillator 0, may be increased Another object of the invention is to beat to, for example, 10,001 kilocycles. It will be understood that a single oscillator may be employed'to' replace the oscillator 0 and the harmonic generator HG, said' oscillator being capable of setting .uphigh frequency oscillations. of similar order, for example, 10,001 kilocycles. The harmonic generator HG is also connected to the input circuit of the detector D The detector D may be a.

vacuum tube detector, or any other device capable of. beating together a plurality of high frequencies so as to obtain a band of.

frequencies which is lower in the frequency spectrum than the high frequencies beaten therein. 7 I i An amplifier A is connected to the output circuit of the detector D This "amplifier may be a vacuum tube amplifier of any well known type, or any amplifier-which can conveniently amplify a plurality of frequencies, such as 49, 50 and 51 kilocycles, which are all located in a single band, without intere modulation between the frequencies of the band. A detector D represents a device which iscapable of detecting a' signal when a plurality of high frequencies are impressed thereon, one of said high frequencies being modulated in accordance vwith the signal. This detector D may be of any well known type, but is preferable a vacuum tube detector. A band filter F is connected to the output circuit of the detector D and is employed for transmitting'a low frequency sig-' nalof. the order of, for example, 1,000 cycles, as derived from the detector D while substantially suppressing all other frequencies. This band filter may be of any well known type, but is preferably of the type disclosed in the patent to A. Campbell No. 1,227,113, dated May 22, 1917. The low frequency signal is then impressed on the channel L. I

The arrangements of Fig. 1 operate in the following manner for the signals: 7 i

A high frequency current is impressed on the receiving circuit comprising the antenna a, the counterpoise b and the inductance 0, and, byvirtue of the coupling existing be tween the inductances c and d, is also imp)ressed on the input circuit of the detector At the same time the oscillator 0 also transmits 'a high frequency current to the inputrcircuitof the detector. D Furtherdetection of I iii more, the oscillator transmits a high frequency current to the harmonic generator HG. which multiplies the frequency of the oscillator 0 and impresses the frequency as thus multiplied upon the input circuit of the detector D Thus the high frequency current upon which the signal is superposed, having a fre quency of 10,000 kilocycles, and the frequency of the oscillator 0 having a frequency of 10,050 kilocycles, and the frequency of the harmonic generator HG, hav-- ing a frequency of 10,001 lrilocycles, are all impressed on the detector D and are there beaten together. As is well known in the art, a band of frequencies, known as the difference band, results therefrom, among other frequencies. The amplifier A amplifies this band of frequencies, which includes the frequencies of 19, 50 and 51 kilocycles, without any intermodulation between these frequencies. The amplifier A may have filtering means included therein for substantially suppressing all frequencies except the frequencies Within the band to be amplified thereby. This band of frequencies is then impressed on the detector D, from which the low frequency signal is derived. All of the products resulting from" detection are then impressed upon the filter F which transmits the low frequency signal through substantially suppressing all other frequencies. The low frequency signal, which may be of the order of 1,000 cycles, then appears in the channel L.

Referring to Fig. 2, there is shown a modification of the arrangements of Fig. 1. The antenna 6 is connected to the inductance 0, and these together form a receiving circuit which is capable of receiving high frequency oscillations of the order of 10,000 kilocycles upon which low frequency signals are superposed. An inductance (J is coupled to the inductance 0 and impresses the received currents on the detector 1),. An oscillator is represented bythe reference character 0 which may be a piezoelectric oscillator, capable of setting up oscillations of the order of 10,001 kilocycles. These oscillations are impressed upon a detector 1),. Connected to the input circuits of the detectors 1) and D is an oscillator 0 which is similar in all respects to the oscillator 0 described hereinabove in connection with Fig. 1. This oscillator O, is also capable of setting up oscillations of the order of 10,050 kilocycles.

The detector D, is employed for beating together thefrequency of the oscillator 0 and the frequency of the current impressed on the receiving circuit which includes the antenna 0 and the inductance c. The detector D is employed for beating together the frequency of the oscillator (1 and the frequency of the oscillator 0 An amplifier A, is employed for amplifying a frequency, known in the art as the difference frequency, for example, 50 kilocycles, resulting from the heating of the frequency of oscillator 0 and the frequency of the receiving circuit. An aznplifier A, is employed for amplifying the difference frequency, for example, 51 kilocycles, resulting from the beating of the frequency of the oscillator 0 and the frequency of the oscillator O These frequencies, as amplified by amplifiers A, and A are impressed on the detector D which derives the low frequency signal by beating these difference frequencies together. The low frequency signal, for example, 1,000 cycles, is then transmitted to the channel L. The detectors D 1),, and D may be similar to the detectors D and described hereinabove in connection with Fig. 1.

The arrangements of Fig. 2 operate in the following manner:

The frequency of the oscillator 0 10,001 kilocycles, beats with the frequency of the oscillator 0,, 10,050 kilocycles in the detector 1),. The frequency of the received currents upon which the signal is superposed, 10,000 kilocycles, also beats with the frequency of the oscillator O in the detector It will benoted. that the frequency of the oscillator O, is very close to the frequency to which the receiving circuit is tuned, and it will also be noted that the oscillator 0 is common to the input circuits of detectors 1),, and 1),. There results from beating these frequencies currents having frequencies of '51 and kilocycles, respectively. The current of 51 kilocycles is impressed on the amplifier A, to be amplified thereby, and the current of frequency 50 kilocycles is impressed on the amplifier A, to be similarly amplified. These frequencies, as thus amplified, beat together in the detector 1), from which the low the quency signal of 1,000 cycles is derived. This low frequency signal is then impressed upon the channel L.

It will be understood that the frequencies employed herein are merely illustrative and that other frequencies may be substituted in practice as conditions necessitate.

1V hile this invention has been disclosed in certain particular embodiments which are deemed desirable, it is to be understood that it is capable of embodiment in other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. A system for detecting a signal which is superposed on a high frequency current which comprises two high frequency oscillators having frequencies differing from each other and from the frequency of a current on which the signal is superposed, means for beating all of said frequencies together to obtain an intermediate bandof frequencies,

iii

and means for detecting the signal from the intermediate band of frequencies.

2. In combination, means to receive a current of high frequency on which alow frequency signal is superposed, a piezo-electric oscillator, a vacuum tube oscillator, means for beating the high frequency current on which the low frequency signal is superposed and the currents ofsaid piezo-electric oscillator and said vacuum tube oscillator,

means for substantially suppressing all fre-f and means to transmit to the exclusion ofv all.

other frequencies a band of frequencies lower in the frequency spectrum than said high frequencies, means for amplifying said band of frequencies, and means for detectinga low frequency signal from said band of frequencies.

4. A radio receiving system comprising means for generating within one frequency band three high frequency currents, one of said high frequency currents being modua; high frequency current upon which an audio frequency signal is superposed, the combination of two oscillation generators lated in accordance with-signals, means for beating said frequencies together to produce another band of frequencies, and means for deriving the signal from said latter band of frequencies.

5. A radio receiving system comprising means for receiving a high frequency current on which signals are superposed, means for generating two high frequencies which are within the same region of the frequency spectrum as the received high frequency current each other, means for putting these frequencies together so as to form a resultant band which is in a different region of the. frequency spectrum, and means for detecting the signals from said resultant band.

6. The method of receiving signals superposed on a high frequency carrier current which consists in beating with said high frequency carrier current the currents of two other high frequencies, the frequencies of said latter currents differing from the fre quency of the carrier current by a small amount, filtering the products of beating so as to obtaintherefrom a band of frequen cies lower in the frequency spectrum than the frequencies of said carrier currents, and

though differing in frequency from' detecting the signals from said band of frequencies.

7. In a short wave signalingsystem, the combination with an antenna for the reception of a' signaling frequency of a receiving circuit comprising a vacuum tube oscilaltor, a piezo-electric oscillator, means for beating the signaling frequency with the frequencies of said vacuum tube oscillator and said piezo-electric oscillator to intermediate frequencies, the frequencies of said vacuum tube oscillator and of said piezoelectric oscillator differing from each other and from the signaling frequency, and means for deriving the signalfrom said band of in termediate frequencies.

- 8. In a'sho'rt wave signaling system, the combination with an antenna for the reception of a signaling frequency of a receivlng;

circuit comprising a piezo-electric oscillator having a periodicity difi'ering from the periodicity of said signaling frequency, a vacuum tube oscillator having a periodicity differing from the-periodicities of said signaling frequency and said piezo-electric oscillator, means for beating cies of said pieZo-electric oscillator with the signaling frequency, means frequency of said vacuum tube oscillator with the signaling frequency, and means for deriving the signal from beating the resultant frequencies.

obtain a band of the frequenfor beating the i 9. In a system for deriving a signal from which have frequencies differing from each other and from the frequency of said received current, means for beating said frequencies together so as to produce a band of frequencies lower in the frequency spectrum than the frequency of said received current,

and means for deriving the audio signal from the lower band of frequencies.

10. The method of. signaling which consists in receiving a high frequency current modulated by a low frequency signaling current, beating therewith the oscillations of two high frequency generators which have frequencies differing from the frequency of the received current by a small amount, filtering so as to obtain ,a bandwhich has frequency limits lower than the frequency of said received current, and demodulating the frequencies of said band so as to obtain the low frequency signaling currents.

In testimony whereof, I have signed my name to this specification this 24th day of August, 1925.

RUSSELL S. OHL.

the products resulting from beating I 

